Optical fibre feed arrangement

ABSTRACT

The present invention concerns a procedure and a system for feeding optical fiber cables into a pipeline with the help of an installation device at adjustable speed. In order to prevent damage during the advancement of the optical fiber cable the engine ( 15 ) of the installation device has been supplied with a friction safety clutch ( 17 ) exerting pressure on a moving coil ( 18, 23 ).

TECHNICAL FIELD OF THE INVENTION

The present invention concerns a method to be used for feeding atadjustable speed of an optical fibre cable into a pipeline/duct, and anarrangement devised for adjustable feeding of an optical fibre cableinto the same. The feeding arrangement and method are primarily intendedto be used for installations of optical fibre cables in pipeline systemslocated outdoors or between residential units and a central unit, suchas between several apartments in an apartment building and a centralcoupling unit located in the house's cellar or similar.

DESCRIPTION OF RELATED ART

It has been known for some time that optical fibres or optical fibrecables can be blown or sucked into pipelines/ducts, either by creatingoverpressure by means of compressed air supply so that the optical fibreor optical fibre cable is blown into the pipeline, or by creatingunder-pressure at the end of the pipeline/duct, so that the opticalfibre or the optical fibre cable is sucked into it.

SUMMARY OF THE INVENTION

In order to simplify the handling of optical fibre cables in connectionwith their feed into pipelines/ducts and to ensure that they are notexposed to undesirable pressure during the feeding process, which couldresult in the bending or breaking of the cables during this process, afeeding device located in the feeding mechanism has been supplied with afriction safety clutch which regulates the feed of the optical fibrecable when feed resistance increases. For additional regulation of theadvancement of the optical fibre cable the feeding mechanism can beregulated by adjusting the air stream and/or the rotation speed of thefeeding wheel. To further facilitate the operation of the feedingarrangement it has been designed as a hand-tool which needs to beconnected to just one or more energy sources.

The invention is described below in more detail with the help of aproposed method of execution and with reference to the enclosed pagescontaining drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1–3 show different views of the feeding device in accordance withthe invention.

FIG. 4 shows the feeding device in perspective.

FIG. 5 shows the feeding device when disassembled.

FIGS. 6 and 7 provide details of how friction safety clutches can bearranged in relation to the feeding device.

DETAILED DESCRIPTION OF EMBODIMENTS

FIGS. 1–5 show how a feeding device can be constructed in accordancewith the invention. The feeding device consists of a handgrip unit 1containing a battery 2 and of a feeding system for optical fibre cables.The feeding arrangement consists in turn of a lower part 3 and an upperpart 4 connected with each other by a guide bar 5 which is furtherequipped with an adjustable positioning screw 6. With the help of thepositioning screw 6 the distance between the upper part and the lowerpart can be regulated, so that the optical fibre cable can be placedcorrectly between the upper and the lower part when open, and when thetwo parts are brought together it will find itself in a groove 7 betweenthe upper part and the lower part. The cross-section of the groove hasbeen designed in such a way as to be able to hold a maximum of thecross-sectional area of the optical fibre cable. At the front of theupper and lower parts removable extension units 8, 9 of suitablematerial have been fastened, which form together a hollow space 10 of acircular cross-section, for example, into which the end of apipeline/duct can be entered, and through which the optical fibre cableis fed. Adjacent to the removable extension units is a space 11 forcompressed air to be supplied for feeding the optical fibre cable intothe pipeline. The lower section of this space is connected to acompressor 12 by means of an adjustment screw 13 for regulation of thesupply of compressed air. The lower section is further connected to ahandgrip unit 1 which can be designed like a pistol-type handle,containing a trigger 14 for the regulation of the number of revolutionsof the engine 15 pushing the optical fibre cable forward. In addition tothe regulator of the rotational frequency the section also contains aswitch for changing the direction of the feed and a resetting device.The engine 15 is fastened to the lower part, and its driving axle 16operates through a friction safety clutch 17 upon a moving coil 18. Theengine can be either electrically driven or it may be powered bycompressed air. Electric operation can be provided by means of arechargeable battery in the battery component 2 fastened to thehandgrip's lower part 1, or it may be connected to an external powersupply via the rotational frequency regulator. When using the electricengine only, the optical fibre cable can be fed into the pipelinewithout any supply of compressed air to the extension units. When theengine is operated by compressed air, its compressor can be connected tothe compressor used for the feeding of the optical fibre into thepipeline. The friction safety clutch 17 ensures controlled forward feedof the optical fibre cable due to the fact that at constant rotation ofthe engine and increased resistance felt by the optical fibre cableduring its forward feed into the pipeline the moving coil will skid inthe opposite direction to the driving axle, preventing the cable frombeing exposed to forces going in the opposite direction, which couldresult in the bending or breaking of the optical fibre cable in the feedarea. By further providing the clutch with a possibility of regulation,a suitable safety level can be achieved for the forward-feed of theoptical fibre cable. Thanks to the flexibility provided by the frictionsafety clutch, the force of the forward motion of the optical fibrecable can be regulated, depending on the resistance encountered in thepipeline, and the forward feed of the cable can thus be optimised.

The friction safety clutch 17 may consist of two circular contactsurfaces 19, 20 made of low-friction material, operating between the endof the driving axle 16 and the moving coil 18 made of metal, as well asbetween the said moving coil and an external plate (21), which isconnected to the driving axle's end by means of adjustment screws 22(see FIG. 6). The contact surfaces can thus be pressed against themoving coil with controlled force. If the feed of the optical fibrecable is obstructed in the pipeline, the contact surfaces of thefriction safety clutch will start skidding against the moving coil,impeding its movement, so that the cable will not be pushed forward atthe risk of being damaged. The friction safety clutch 17 may alsoconsist of a moving coil 23 made of low-friction material, operatingbetween the driving axle's end 16 and an external, spring-loaded 24plate 25 made of, for example, metal. The force exerted by the springcan be regulated by means of a screw 26 in order to attain a desirabledegree of friction by the clutch, thus preventing damage of the opticalfibre cable during its forward feed into the pipeline.

The upper part contains further a spool holding device 27, 28 with aspool support 29 on which a spool with an optical fibre cable can befastened. The holding device for the spool arm has been designed in sucha way that the position of the spool arm can be adjusted as desired. Theupper part contains also a revolution counter 30. With the help of therev. counter the number of revolutions may be counted, or the length ofthe optical fibre cable fed into the pipeline measured by means of ameasuring wheel 31 which is turned by the running optical fibre cablebeing fed into the pipeline. The measuring wheel can be spring-loaded,so that the pressure of the optical fibre cable which is being fed intothe pipeline can be regulated, which helps to ensure that the cableadvances correctly. The measuring wheel should preferably be madeconspicuous and contain some sort of marking, so that the wheel'srotations can be observed, which is of great use to the user of theinstallation device. This can be done by providing a transparent lock 32for the measuring wheel, ensuring its protection and visibility of itsrotations. The user will thus be able to see whether the measuring wheelis rotating or not during the forward feed of the optical fibre cable bythe moving coil, which is why it is a good idea to provide also themoving coil with some visible marking so that its rotations can beobserved. This can be done by supplying a transparent lock 33 for themoving coil so that it can be protected and visible.

The installation device may either be held by hand or it may be placedon a tripod. A roll of optical fibre cable is placed on the spool armand one end of the cable is introduced into the groove space between theupper and the lower part. To regulate the distance between the upper andthe lower part a positioning screw is used for the raising or loweringof the upper part in relation to the lower part. When the two parts arebrought together the measuring wheel will press the optical fibretowards the moving coil with the help of the spring. The optical fibrecable is further led through the interacting removable extension units,and its one end is stuck into a pipeline which has been placed in theextension units. When the engine is started and compressed air issupplied, the optical fibre cable will be fed into the pipeline.Depending on the feed requirements the positioning screws are adjustedin a suitable way, and an operator may monitor the feed.

When a tripod is used, the installation device can be manoeuvred from adistance with a remote control 34. Once suitable air supply and adesirable degree of friction has been ensured with the help of theadjustment screws, the installation device placed on a tripod may easilybe manoeuvred by means of the remote control, and the operator has moretime to watch over and regulate the forward feed of the cables. Theinvention is, naturally, not limited to the above-described method ofexecution illustrated in the drawings, and can be modified within theframework of the attached patent claims.

1. An apparatus for feeding an optical fibre cable into a pipeline,comprising: a feeding device having an upper part and a lower partwherein when the upper part is joined to the lower part, a forwardportion of the feeding device forms a hollow space for feeding theoptical fibre cable into the pipeline and a remaining portion of thejoined upper and lower part forms a groove for receiving the opticalfibre cable; an engine coupled to the groove for advancing the opticalfibre cable through the hollow space into the pipeline; a frictionsafety clutch connected to the engine for regulating the forward feed ofthe optical fibre cable when feed resistance in the pipeline increases.2. The apparatus of claim 1, further comprising; a receptacle forreceiving compressed air into the feeding device's hollow space forregulating advancement of the optical fibre cable into the pipeline. 3.The apparatus of claim 1, wherein the friction safety clutch comprises:contact surfaces comprising low-friction material for pressing againstboth sides of a moving coil connected to the engine for feeding theoptical fibre cable through the groove into the hollow space; and meansfor adjusting operation of the safety clutch according to the opticalfibre cable used and according to the pipeline parameters.
 4. Theapparatus of claim 3, wherein force for pressing against either side ofthe moving coil is regulated to attain a controlled degree of frictionby the friction safety clutch.
 5. The apparatus of claim 1, wherein theengine is operated by compressed air.
 6. The apparatus of claim 1,wherein the engine is an electrical motor.
 7. The apparatus of claim 1,wherein the hollow space comprises a circular cross section capable ofreceiving the end of the pipeline.
 8. The apparatus of claim 1, furthercomprising a measuring wheel for registering the length of the cableinto the pipeline, wherein the measuring wheel can regulate pressureexerted on the optical fibre cable being fed into the pipeline.
 9. Amethod for feeding an optical fibre cable into a pipeline, comprisingthe steps of: utilizing a feeding device having a groove connected to ahollow space both formed by an upper and lower part, wherein the hollowspace is for receiving the optical fibre cable from the groove andconnecting the feeding device to the pipeline; advancing the opticalfibre cable through the hollow space into the pipeline utilizing anengine coupled to the groove; and regulating the forward feed of theoptical fibre cable when feed resistance increases in the pipeline,using a friction safety clutch connected to the engine.
 10. The methodof claim 9, further comprising the step of: receiving compressed airinto the feeding device's hollow space for regulating advancement of theoptical fibre cable into the pipeline.
 11. The method of claim 9,wherein the step of regulating the forward feed of the optical fibrecable using a friction safety clutch connected to the engine when feedresistance increases, further comprises: the friction safety clutchpressing against both sides of a moving coil, connected to the engine,for advancing the optical fibre cable through the groove and the hollow.12. The method of claim 11, further comprising: regulating force on themoving coil using the friction safety clutch against both sides of themoving coil to attain a controlled degree of friction.
 13. The method ofclaim 9, wherein the engine is operated by compressed air.
 14. Themethod of claim 9, wherein the engine is an electrical motor.
 15. Themethod of claim 9, further comprising; receiving the end of the pipelineinto the hollow space; the optical fibre feeding into the groove at aback portion of the feeding device, advancing the optical fibre cablethrough the groove into the hollow space utilizing the engine and themoving coil; and receiving compressed air for regulating forward feedingof the optical fibre cable into the pipeline.